Vienna aka Viennese

[Burgerman]

So it's longevity/cost vs weight.

If you want it to last (longevity) you need more Ah, and a proper cell balancing charger, and no BMS. And those are not cheap for 12Ah!

[biscuit]

Yup. Been putting off making a battery pack so long it's now got more difficult. But just as necessary.

[Burgerman]

IF it were me, and you are only looking for a small light battery, I might use 4 of these. But not cheap. https://hobbyking.com/en_us/zippy-fligh ... -xt90.html

Instead of 1C and 20A capable, like the ones in your link, these are 30C. So can do hundreds of amps. They therefore do not need a BMS to protect them fom high currents and will not cut out. They will last well because you will be using a hobby charger to charge them. The only danger is over discharge, so you will need to monitor them. But again, this gives only 17Ah.
https://hobbyking.com/en_us/zippy-fligh ... -xt90.html

There may be better prismatic cells that will let you do better.

[biscuit]

For better or for worse, I've got 9x 40ah prismatic LiFeP04 cells being shipped to me as we speak. The chair has a VSI controller. If all 9 cells are good, would the VSI manage 3.2V x 9 = 28.8V, if I made a 9s battery? My plan was an 8s battery and I had no faith in the cells so I ordered 1 spare, but the extra cell would be... spare. So, ignoring the charging/ balancing/ space issues for the moment, is 9s a possibility?

When I say for better or for worse, I mean Headways might have been better, as I can't use my battery box anyway. And the big hurdles for me have got much smaller, they were soldering and my comfort zone (hahaha not sure Anybody on this board keeps to their comfort zone, if they even have one!)

[Burgerman]

9 too many. Too high voltage. 3.6v x 9 when charging/charged is over 32.4 volts. It may or may not give errors. It may only error on downhill or deceleration.

8 is already higher voltage than 24v lead bricks. And it stays this way through 80% of the charge.

And 9 cannot be charged via PL8. So whats the plan?

[biscuit]

No plan for a 9s any more. It was just a thought flying through my skull stuffing, anyway. I'll have a spare cell, is all. The battery will be 8s1p. All the info for making up a battery is already on this forum. Charging it is another learning curve.

I got these cells:
￡46.25 | 1pcs New Energy Lifepo4 40Ah 3.2v 40ah Cell Supercapacitor Li-ion 100A Discharge for EV Pack Diy Solar Battery Hard Case Proof
https://s.click.aliexpress.com/e/cfocnxy4

[Burgerman]

20Ah stock battery

That will actually give you half that in real world high discharge rate conditions. So 40Ah lithium will give you a real 40Ah. Say 35Ah safe usable. So 3.5X range increase.